KR101447110B1 - Lead-free and cadmium-free electroless plating solution, method of electroless plating using the same, and nickel plating layer using the same - Google Patents

Abstract

The present invention provides a lead-free and cadmium electroless nickel plating solution that is environmentally friendly and has improved nickel plating solution stability and provides excellent plating properties. A lead-free and cadmium electroless nickel plating solution according to an embodiment of the present invention includes a nickel metal salt that provides nickel ions for plating; A reducing agent for reducing nickel ions for plating; A complexing agent which forms a complex with a nickel ion for plating and contains a carboxylic acid and an aliphatic acid; And a metal stabilizer which suppresses the reduction reaction of nickel ions for plating and is lead-free and cadmium free and contains a metal element.

Description

TECHNICAL FIELD [0001] The present invention relates to a lead-free and cadmium-free electroless plating solution, a method of electroless plating using the same, and a nickel plating layer using the same same}

Technical aspects of the present invention relate to electroless plating, and more particularly, to a lead-free and cadmium electroless nickel plating solution, an electroless plating method, and a nickel plating layer.

Electroless plating is a method in which a metal plating layer is formed on an object to be plated by the oxidation / reduction reaction of metal, and plating can be performed irrespective of the shape of the product and after the specific pretreatment, It is used in industrial fields.

Plated surfaces using electroless plating are becoming increasingly important in the parts and materials industry, such as in mounting surfaces such as ultra-small devices with high density in various packaging fields and in bonding interfaces. In recent years, there has been a demand for an increase in the internal circuit density and a narrow pitch in accordance with the weight reduction, miniaturization and high performance of electronic products. Therefore, there is a need for an electroless plating method in which the variation in the thickness of the plating layer is small, Is increasing.

Particularly, since the plating film formed by the electroless nickel plating method can control the deposition amount of phosphorus formed by the vacancy reaction, it is possible to form the plating layer having the amorphous alloy and have the plating layer having the uniform surface, A plating layer excellent in corrosion resistance, abrasion resistance and the like can be formed. Therefore, the electroless nickel plating method is widely applied as a plating technique for final surface treatment of automobiles, precision machine parts, electronic parts such as semiconductors and printed circuit boards (PCB). In addition, application fields such as a bad treatment of soldering of a printed wiring board or a primary treatment of a compact disk (CD) or a hard disk drive (HDD) have been broadened.

In the case of using the electroless nickel plating method, it is necessary to suppress the reduction reaction from occurring in a region other than the surface of the object to be plated. To this end, a stabilizer such as a lead (Pb) compound or a cadmium (Cd) Inhibitor). However, since lead (Pb) and cadmium (Cd) are prohibited or restricted from being used as environmentally regulated substances, a substance to replace them is required, and some of them are commercially used.

However, Pb-free or Cd-free electroless nickel plating solutions currently used have low stability and cause self-decomposition of the nickel plating solution or adsorption of fine particles generated in the nickel plating solution to the plating film, There is a limit such that defects such as generation of pits occur. As a result, the efficiency of the nickel plating solution is reduced to lower the productivity, and the lifetime of the nickel plating solution is shortened, thereby increasing environmental costs such as plating wastewater treatment. Further, when plating copper wirings such as a package substrate and a printed circuit board (PCB), there arises a problem that a thickness variation occurs in parts such as the top, side, and edge faces, resulting in poor solderability and poor corrosion resistance.

The technical object of the present invention is to provide a lead-free and cadmium-free electroless nickel plating solution which is environmentally friendly and has improved nickel plating solution stability and provides excellent plating properties.

SUMMARY OF THE INVENTION The present invention provides an electroless plating method using an electroless nickel plating solution which is environmentally friendly and has improved nickel plating solution stability and provides excellent plating characteristics.

The technical problem to be solved by the present invention is to provide a nickel plated layer formed by using the lead-free and cadmium electroless nickel plating solution

However, these problems are illustrative, and the technical idea of the present invention is not limited thereto.

According to an aspect of the present invention, there is provided a lead-free and cadmium electroless nickel plating solution comprising: a nickel metal salt for providing nickel ions for plating; A reducing agent for reducing nickel ions for plating; A complexing agent which forms a complex with nickel ions for plating and comprises a carboxylic acid and an alpha hydroxy acid; And a metal stabilizer which suppresses the reduction reaction of nickel ions for plating and is lead-free and cadmium-free and contains a metal element.

In some embodiments of the present invention, the complexing agent is included in the range of 20 g to 40 g per liter of the nickel plating solution.

In some embodiments of the present invention, the complexing agent may include the carboxylic acid in the range of 5 g to 25 g per 1 liter of the nickel plating solution, and the aliphatic acid in the range of 5 g to 20 g .

In some embodiments of the present invention, the complexing agent is at least one selected from the group consisting of acetic acid, adipic acid, tartaric acid, and succinic acid derivatives of the carboxylic acid and derivatives of the above-mentioned alpha hydroxy acid, citric acid, lactic acid, glycolic acid , And mandelic acid may be mixed with each other.

In some embodiments of the present invention, the complexing agent includes 5 to 25 g of adipic acid and acetic acid per 1 liter of the nickel plating solution, and 5 to 20 g of lactic acid.

In some embodiments of the present invention, the complexing agent includes adipic acid, acetic acid, and tartaric acid in an amount ranging from 5 g to 25 g per 1 liter of the nickel plating solution, and may include lactic acid in the range of 5 g to 20 g .

In some embodiments of the present invention, the complexing agent comprises adipic acid, acetic acid, and succinic acid in an amount ranging from 5 g to 25 g per 1 liter of the nickel plating solution, and the total amount of lactic acid and glycolic acid is in the range of 5 g to 20 g Can include

In some embodiments of the present invention, the complexing agent includes adipic acid and acetic acid in an amount of 5 g to 25 g per 1 liter of the nickel plating solution, and further includes lactic acid and thiodiglycolic acid in a range of 5 g to 20 g can do

In some embodiments of the present invention, the nickel metal salt may comprise at least one of nickel sulfate, nickel chloride, nickel sulfamide, nickel nitrate, nickel oxide and nickel carbonate. The nickel metal salt may be included in the range of 4 g to 7 g per liter of the nickel plating solution

In some embodiments of the present invention, the reducing agent may include at least one of hypophosphite, boron hydride, dimethylamine borane, and hydrazine. The reducing agent may be included in the range of 20 g to 35 g per 1 liter of the nickel plating solution.

In some embodiments of the present invention, the metal stabilizer is at least one of a metal selected from the group consisting of Tel, Te, Sn, Sn, . ≪ / RTI >

In some embodiments of the present invention, the metal stabilizer may include at least one of a metal element itself, a nickel metal salt, a metal oxide, and a metal sulfide.

In some embodiments of the present invention, the metal stabilizer may be included in the range of 0.1 ppm to 5.0 ppm based on 1 liter of the nickel plating solution.

In some embodiments of the present invention, the metal stabilizer may be previously dissolved in an alkylsulfonic acid solution and added to the nickel plating solution.

In some embodiments of the present invention, the pH of the nickel plating solution is adjusted to be in the range of 3.5 to 5.5 and further includes a pH adjusting agent containing at least one of sulfuric acid, hydrochloric acid, nitric acid, ammonia water, sodium hydroxide, can do.

In some embodiments of the present invention, a sulfide-based stabilizer for inhibiting spontaneous decomposition of the nickel plating solution and preventing the precipitate formed by aging of the nickel plating solution from reacting with the reducing agent to stabilize the nickel plating solution .

In some embodiments of the present invention, the sulfide-based stabilizer comprises at least one of thiourea and derivatives thereof, sulfite, pyrosulfite, and thiocyanate .

In some embodiments of the present invention, the sulfide-based stabilizer may be included in the range of 0.1 ppm to 3.0 ppm based on 1 liter of the nickel plating solution.

The lead-free and cadmium electroless nickel plating solution according to the technical idea of the present invention does not contain lead (Pb) and cadmium (Cd), which are environmentally harmful substances, but instead contains telenium (Te), selenium (Se) (Sn), tin (Tl), molybdenum (Mo), and the like as stabilizers, it is possible to provide an environmentally friendly nickel plating solution and to prolong the life of the nickel plating solution, Uniformity of the entire plating layer including the edge portion can be provided.

By performing the plating process using the nickel plating solution of the present invention, the lifetime of the plating solution itself is increased, and the efficiency and productivity of the plating process can be improved. Also, the change in the characteristics of the plating film due to the increase in the number of turns (MTO) And an amorphous plating film which is free of pits and is not crystal grains can be formed according to an increase in the number of turns. In addition, the plating layer has excellent hardness, wear resistance, mechanical properties and corrosion resistance, and can maintain a stable nickel plating solution even at a plating time of 8 times or more and can have a plating rate as high as about 10 占 퐉 / hr, have.

In addition, by performing the electroless plating process using the nickel plating solution of the present invention, when plating is performed on the surface of the material having a shape with a large irregularity and bending, a plating layer having a constant thickness can be formed irrespective of the shape of the surface of the plating target Therefore, it is possible to minimize the defective rate according to the thickness of the plating layer, and it is possible to provide a uniform plating characteristic particularly at the corners where the coating property is poor.

The effects of the present invention described above are exemplarily described, and the scope of the present invention is not limited by these effects.

1 is a schematic view showing a plating apparatus using a lead-free and cadmium electroless nickel plating solution according to an embodiment of the present invention.
2 is a flowchart illustrating an electroless plating method using a lead-free and cadmium electroless nickel plating solution according to an embodiment of the present invention.
FIG. 3 is a graph showing the plating rate obtained in the process of plating the plating target using the nickel plating solution according to the technical idea of the present invention and the nickel plating solution according to the comparative example, according to the plating number.
FIG. 4 is a graph showing the amount of phosphorus deposited in the plating layer formed in the process of plating the plating object using the nickel plating solution according to the technical idea of the present invention and the nickel plating solution according to the comparative example, according to the plating number.
5 is a scanning electron micrograph showing the surface of the plating layer formed on the plating target object according to the number of times of plating using the nickel plating solution according to the technical idea of the present invention and the nickel plating solution according to the comparative example, respectively.
6 is a scanning electron microscope (SEM) image of a plating layer formed on a copper wiring of a printed circuit board using a nickel plating solution according to the technical idea of the present invention and a nickel plating solution according to a comparative example, respectively.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. It will be apparent to those skilled in the art that the present invention may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the concept of the invention to those skilled in the art. The scope of technical thought is not limited to the following examples. Rather, these embodiments are provided so that this disclosure will be more thorough and complete, and will fully convey the scope of the invention to those skilled in the art. As used herein, the term "and / or" includes any and all combinations of one or more of the listed items. The same reference numerals denote the same elements at all times. Further, various elements and regions in the drawings are schematically drawn. Accordingly, the technical spirit of the present invention is not limited by the relative size or spacing depicted in the accompanying drawings.

1 is a schematic view showing a plating apparatus using a lead-free and cadmium electroless nickel plating solution according to an embodiment of the present invention.

1, the plating apparatus 10 includes an electroless nickel plating solution 30 containing a lead-free and cadmium electroless nickel plating solution 30 in a plating bath 20, and an electroless nickel plating solution 30, Thereby forming a plating layer 50 on the plating target body 40. [0051] Hereinafter, the lead-free and cadmium free electroless nickel plating solution 30 will be referred to as a nickel plating solution 30 for the sake of simplicity. Also, the case of using a metallic nickel plating solution other than the nickel plating solution 30 is also included in the technical idea of the present invention.

The nickel plating solution 30 includes a solvent and a nickel metal salt, a reducing agent, a complexing agent, and a metal stabilizer dissolved in the solvent. Further, the nickel plating solution 30 may further include a pH adjusting agent. The nickel plating solution 30 suppresses the natural decomposition of the nickel plating solution 30 and prevents the precipitate formed by the aging of the nickel plating solution 30 from reacting with the reducing agent to stabilize the nickel plating solution 30 Based stabilizer capable of functioning as a stabilizer. Further, the nickel plating solution 30 may further include an auxiliary additive composed of an organic compound or an inorganic compound for controlling the plating rate and improving the gloss characteristics. Further, the nickel plating liquid 30 may further include a surfactant for improving the interfacial property between the matrix layer and the plating layer and for preventing pit formation.

The plating object 40 may include a metal or a polymer material. The plating object 40 may include, for example, copper or iron.

The nickel plating solution 30 may have a pH ranging from 4.0 to pH 5.0, and the plating process may be performed at 75 to 90 ° C.

Hereinafter, the constituent elements of the nickel plating liquid 30 will be described in detail.

The solvent can constitute most of the nickel plating liquid 30 in which the plating target object 40 is immersed. The solvent may include a material that dissolves the nickel metal salt, the reducing agent, the complexing agent, and the metal stabilizer, the pH adjuster, and the sulfide stabilizers. The solvent may be, for example, water. However, this is illustrative and the technical idea of the present invention is not limited thereto.

The nickel metal salt may be dissolved in the solvent. The nickel metal salt may provide nickel ions for plating to the plating object 40, and the plating nickel ions may form the plating layer 50 on the plating target object 40. The nickel metal salt may include a metal, for example, nickel (Ni). Accordingly, the nickel ions for plating may include nickel (Ni) ions, and the nickel ions may be, for example, bivalent ions. The nickel metal salt may include, for example, a nickel salt hydrate and may include at least one of, for example, nickel sulfate, nickel chloride, nickel sulfide, nickel nitrate, nickel oxide, and nickel carbonate. For example, the nickel sulfate can be obtained by dissolving nickel, nickel oxide, or nickel carbonate in sulfuric acid and evaporating it at room temperature, thereby precipitating in a green needle crystal (orthorhombic) of the rhizome.

The nickel metal salt may be included in the range of 4 g to 7 g per liter of the nickel plating solution (30). For example, when the nickel metal salt is nickel sulfate, if the concentration of nickel sulfate is less than 4 g / liter, the plating rate may be lowered. If the concentration of nickel sulfate exceeds 7 g / liter, the stability of the nickel plating solution may be lowered, and spontaneous decomposition of the nickel plating solution may occur.

The reducing agent may be dissolved in the solvent. The reducing agent may reduce the nickel ion for plating. The reducing agent may reduce the nickel ion, for example. The reducing agent may include at least one of hypophosphite, boron hydride, dimethylamine borane, and hydrazine. The reducing agent may include at least one of sodium hypophosphite, potassium hypophosphite, and ammonium hypophosphite as the hypophosphite. By including such a reducing agent, the nickel plating solution can contain about 7% to about 9% phosphorus (P).

The reducing agent may be included in the range of 20 g to 35 g per 1 liter of the nickel plating solution (30). For example, when the reducing agent is sodium hypophosphite, the plating rate may be lowered when the concentration of sodium hypophosphite is less than 20 g / liter. If the concentration of the sodium hypophosphite is more than 35 g / liter, the stability of the nickel plating solution is lowered, and spontaneous decomposition of the nickel plating solution may occur.

The complexing agent may be dissolved in the solvent. The complexing agent may form a complex with the nickel ion for plating. For example, the complexing agent may be chemically bonded to the nickel ion to form a nickel complex. The stability characteristics of the nickel plating solution 30 and the characteristics of the plating layer 50 are greatly changed depending on the kind and amount of the complexing agent and therefore it is very important to select the type and amount of the complexing agent depending on the purpose and use of the complexing agent. The complexing agent controls the plating rate, prevents spontaneous decomposition of the nickel plating solution 30, and controls the plating reaction so that the reduction reaction of nickel occurs smoothly on the surface of the plating target body 40. The complexing agent is capable of controlling the total amount of nickel ions participating in the reduction reaction with organic acids or their salts and preventing the nickel ions from being precipitated as nickel phosphate by binding with phosphorus so that the nickel plating solution 30 It is possible to perform a function of maintaining stability. In addition, the complexing agent reduces the rapid formation of hydrogen ions by the reduction reaction, so that the pH of the nickel plating solution 30 can be prevented from changing abruptly.

The complexing agent may be at least one selected from the group consisting of a carboxylic acid having a carboxyl group (COOH) and at least one of the derivative thereof and an alpha-hydroxy acid (AHAs) in which a part of the carboxyl group (COOH) is substituted with a hydroxyl group And may include at least any one of them.

The complexing agent may be a carboxylic acid or a derivative thereof such as acetic acid, adipic acid, formic acid, propionic acid, butyric acid, valeric acid, the present invention relates to a process for the preparation of a compound of formula (I) wherein R is selected from the group consisting of an acid, caproic acid, enanthic acid, caprylic acid, pelargonic acid, capric acid, undecylic acid, but are not limited to, lauric acid, tridecylic acid, myristic acid, pentadecanoic acid, palmitic acid, margaric acid, stearic acid, Tartaric acid, succinic acid, glutaric acid, pimelic acid, tartaric acid, tartaric acid, tartaric acid, succinic acid, malic acid, Such as suberic acid, azelaic acid, sebacic acid, ortho-phthalic acid, isophthalic acid, Or at least one of terephthalic acid, maleic acid, fumaric acid, glutaconic acid, traumatic acid, and muconic acid. can do.

The complexing agent may be at least one selected from the group consisting of glycolic acid, lactic acid, citric acid, and mandelic acid as the alpha hydroxy acid and derivatives thereof .

For example, the complexing agent may be at least one selected from the group consisting of citric acid, lactic acid, glycolic acid, and mandelic acid, derivatives of aliphatic acid and at least one of acetic acid, adipic acid, tartaric acid, May be mixed with at least one of them.

The complexing agent may be included in the range of 20 g to 40 g per liter of the nickel plating solution (30). When the concentration of the complexing agent is less than 20 g / liter, the stability of the nickel plating solution is lowered, and spontaneous decomposition of the nickel plating solution may occur. When the concentration of the complexing agent is more than 40 g / liter, the stability of the nickel plating solution is increased, but the plating rate can be reduced. If the plating rate is decreased, the production time may become long, and the economical efficiency and the product characteristics may be deteriorated. As the number of plating times is increased, the decomposition complex agent is present as a suspended substance in the nickel plating solution to reduce the lifetime of the nickel plating solution . The complexing agent may be a mixture of various kinds of materials depending on the purpose of use and the characteristics of the object to be plated. For example, two or five kinds of materials may be mixed.

For example, the complexing agent may include the carboxylic acid in an amount of 5 g to 25 g and the aliphatic acid in an amount of 5 g to 20 g based on 1 liter of the nickel plating solution (30).

For example, the complexing agent may include adipic acid and acetic acid in an amount of 5 g to 25 g, and lactic acid in an amount of 5 g to 20 g, per 1 liter of the nickel plating solution (30). Herein, the adipic acid and acetic acid are derivatives of the carboxylic acid. Further, the lactic acid is a derivative of the above-mentioned aliphatic acid.

Further, in order to increase the stability of the nickel plating solution 30 and improve the plating rate, the complexing agent may further include tartaric acid which is a derivative of the carboxylic acid. For example, the complexing agent may include adipic acid, acetic acid, and tartaric acid in an amount ranging from 5 g to 25 g per 1 liter of the nickel plating solution (30), and the complexing agent may include the lactic acid in the range of 5 g to 20 g .

In order to suppress the decomposition of the nickel plating solution 30 during the plating process or increase in the number of times of plating (MTO), and to maintain the stability of the nickel plating solution 30 and the plating rate, the complexing agent is a succinic acid derivative of the carboxylic acid And glycolic acid as a derivative of the above-mentioned alpha-hydroxy acid. For example, the complexing agent may include adipic acid, acetic acid, and succinic acid in an amount of 5 g to 25 g per 1 liter of the nickel plating solution (30), and the complexing agent may include 5 to 20 g of lactic acid and glycolic acid Range. ≪ / RTI >

Further, for example, the complexing agent may include adipic acid, acetic acid, tartaric acid, and succinic acid in an amount of 5 g to 25 g per 1 liter of the nickel plating solution (30), and the complexing agent may include the lactic acid and the glycolic acid 5 g to 20 g.

Further, in order to increase the stability of the nickel plating solution 30 and to prolong the lifetime, the complexing agent may further include thiodiglycolic acid, which is a derivative of the above-mentioned alpha-hydroxy acid. For example, the complexing agent may include adipic acid and acetic acid in an amount ranging from 5 g to 25 g per 1 liter of the nickel plating solution (30), and the complexing agent may contain the lactic acid and thiodiglycolic acid in the range of 5 g to 20 g . The thiodiglycolic acid may be included in the range of 0.1 g to 5 g.

When the complexing agent contains thiodiglycolic acid, it is preferable that the carboxylic acid includes adipic acid, acetic acid, and tartaric acid in a total amount of 5 g to 25 g, or the carboxylic acid includes adipic acid, acetic acid, tartaric acid, Succinic acid in a total amount of 5 g to 25 g, or in the range of 5 g to 20 g of lactic acid and thiodiglycolic acid as the aliphatic acid.

Hereinafter, the metal stabilizer contained in the nickel plating solution 30 will be described.

In the electroless plating, the reduction reaction of nickel ions for plating, for example, nickel, should be controlled so that the precipitation rate can be predicted, and the reaction should be controlled to occur only on the surface of the object to be plated. To this end, stabilizers that inhibit the reduction reaction may be added to the nickel plating solution. The nickel plating solution which does not contain such a stabilizer itself is unstable, so that nickel itself can be precipitated in the nickel plating solution or on the wall of the plating bath, so that the nickel plating solution may lose its original function. The decomposition of the nickel plating solution can be triggered by colloidal particles or suspended particles existing in the nickel plating solution, and the particles can be introduced from the outside into the impurities, or the concentration of the phosphonic acid used as the reducing agent may be limited by the solubility limit ≪ / RTI > Since the particles have a very large specific surface area, they act as a catalyst for the reduction reaction so that the reaction is successively caused to precipitate nickel, and a large amount of hydrogen gas is released by the reduction reaction to form a fine black precipitate. . In order to suppress the reduction reaction from occurring other than the surface of the plating target, a metal stabilizer containing a metal element is used. As typical examples, a lead (Pb) compound and a cadmium (Cd) compound are used. When lead (Pb) or cadmium (Cd) is added as the metal stabilizer contained in the nickel plating solution, the gloss of the plating layer formed on the plating target is high and stability of the nickel plating solution is improved and widely used. However, such lead and cadmium are environmentally regulated substances and their use should be restricted. Accordingly, the electroless nickel plating solution according to the technical idea of the present invention may have lead-free and cadmium-free characteristics that do not include lead and cadmium.

The metal stabilizer may be dissolved in the solvent. The metal stabilizer can suppress the reduction reaction of nickel ions for plating. In particular, the metal stabilizer can perform the function of stabilizing the nickel plating liquid 30 by suppressing the reduction reaction in a region other than a region where the plating layer 50 of the plating target object 40 is desired to be formed. The metal stabilizer may include a metal element, and may have lead-free and cadmium-free characteristics, particularly free from lead and cadmium. The metal stabilizer may include at least one of a metal element which is the metal itself, a nickel metal salt including the metal element, a metal oxide containing the metal element, and a metal sulfide including the metal element. The metal stabilizer may include at least one of, for example, Telenium (Te), Selenium (Se), Bi (Bi), Sn (Sn), Thallium (Tl), and Molybdenum (Mo).

In order to prevent the metal stabilizer from being released in the nickel plating solution 30 and acting as an impurity, the metal stabilizer is previously dissolved in a strong alkaline solution such as a strong acid solution such as hydrochloric acid or nitric acid or a caustic soda solution to prepare a nickel plating solution 30, ≪ / RTI > The metal stabilizer may be added to the nickel plating solution 30 by previously dissolving it in, for example, an alkyl sulfonate solution. The stabilizer may be previously dissolved, for example, in a solution of methanesulfonic acid in the alkylsulfonic acid solution. In this case, improvement of the properties of the plating layer such as glossiness and the like can be shown.

The metal stabilizer may be included in the range of 0.1 ppm to 5 ppm based on 1 liter of the nickel plating solution (30). That is, the metal stabilizer may be contained in the range of 0.1 mg to 5 mg per 1 liter of the nickel plating solution (30). If the concentration of the metal stabilizer is less than 0.1 ppm, the stability of the nickel plating solution 30 may deteriorate and the gloss of the plating layer may be deteriorated. If the concentration of the metal stabilizer is more than 5.0 ppm, May be deteriorated.

The pH adjusting agent may be dissolved in the solvent. The plating layer 50 formed on the plating target object 40 is affected by the plating speed and the thickness of the plating layer due to the pH of the nickel plating solution 30. Therefore, it is possible to control the pH of the nickel plating solution 30 Is preferably added. Therefore, the pH adjuster may be added to the nickel plating solution 30 as a substance that performs this function. The pH adjusting agent may adjust the pH of the nickel plating solution 30. The pH adjusting agent may include an acidic substance such as sulfuric acid, hydrochloric acid, nitric acid, or the like, or a basic substance such as ammonia water, sodium hydroxide, and potassium hydroxide.

The amount of the pH adjusting agent added to the nickel plating solution may be adjusted so as to maintain the pH of the nickel plating solution 30 in the range of 3.5 to 5.5. When the pH range of the nickel plating solution 30 is 3.5 to 5.5, the nickel plating solution 30 can be more stably maintained, and a plating layer of high quality can be obtained at a high plating rate.

The sulfide stabilizer inhibits the natural decomposition of the nickel plating solution 30 and prevents the precipitate formed by aging of the nickel plating solution 30 from reacting with the reducing agent to stabilize the nickel plating solution 30 can do. The sulfide-based stabilizer may include, for example, a sulfide-based compound. The sulfide stabilizer may include at least one of thiourea and derivatives thereof, sulfite, pyrosulfite, and thiocyanate.

The sulfide stabilizer may be included in the range of 0.1 ppm to 3 ppm relative to 1 liter of the nickel plating solution (30). That is, the sulfide stabilizer may be included in the range of 0.1 mg to 3 mg per 1 liter of the nickel plating solution (30). When the sulfide stabilizer is less than 0.1 ppm, the stability of the nickel plating solution may be lowered. If the sulfide-based stabilizer exceeds 3.0 ppm, pits may be formed in the plating layer, and coarse and non-uniform crystal grains may be formed in the plating layer to deteriorate the properties of the plating layer.

2 is a flowchart showing an electroless plating method (S1) using a lead-free and cadmium electroless nickel plating solution according to an embodiment of the present invention.

2, the electroless plating method S1 includes the steps of preparing a lead-free and cadmium electroless nickel plating solution as described above (S10), and immersing the plating target in the lead-free and cadmium electroless nickel plating solution, And forming an electroless plating layer on the plating object (S20).

Experimental Example

In order to examine the characteristics of the lead-free and cadmium-free electroless nickel plating solution according to the technical idea of the present invention, a plating experiment was conducted.

The nickel plating solution according to the technical idea of the present invention was prepared by using water as a solvent and adding about 5 g of nickel sulfate as a nickel plating solution to 1 liter of nickel plating solution and adding about 30 g of hypophosphite as a reducing agent to 1 liter of nickel plating solution. The complexing agent added to the solvent was configured to contain about 10 g of adipic acid, about 10 g of acetic acid, and about 10 g of lactic acid per liter of the nickel plating solution. Further, about 2 ppm of bismuth (Bi) was added as a metal stabilizer to 1 liter of the nickel plating solution. The bismuth was previously dissolved in the alkylsulfonic acid and added to the nickel plating solution. Further, about 2 ppm of thiourea was added as a sulfide stabilizer to 1 liter of the nickel plating solution. The pH of the nickel plating solution was maintained at about 4.5 using ammonia water. For the nickel plating solution, nickel concentration in the nickel plating solution was analyzed every 30 minutes to replenish the nickel plating solution.

The nickel plating solution used as a comparative example was a commercially available lead-free electroless nickel plating solution. The nickel plating solution used as a comparative example is the product number ECO NP 309 manufactured by Ecostar Co., and is commercially available.

The plating object to be plated in the nickel plating liquid according to the technical idea of the present invention and the nickel plating liquid in the comparative example was prepared through the following process. The iron (Fe) material for the Hull cell test was immersed for 5 minutes using 10% sulfuric acid to remove zinc coated on the surface. The iron material was washed with distilled water. In order to improve the adhesion of the plating layer, soft etching treatment and water washing treatment were performed at a temperature range of 20 to 30 占 폚 for 2 minutes to prepare a plating target. Thereafter, the plating object was immersed in a nickel plating solution to be plated. The temperature of the nickel plating solution during plating was kept constant at about 85 ° C using a hot water bath method. The pH of the nickel plating solution was kept constant at about 4.5 using ammonia water. Nickel salt analysis of the nickel plating solution for replenishing the nickel plating solution And supplemented every 30 minutes. In the present specification, the "number of plating times" is defined as the number of repetitions using the nickel plating solution.

FIG. 3 is a graph showing the plating rate obtained in the process of plating the plating object using the nickel plating solution according to the technical idea of the present invention and the nickel plating solution according to the comparative example, according to the metal turnover (MTO).

Referring to FIG. 3, in the case of the comparative example, the initial plating rate was 13.5 占 퐉 / hr, but the plating rate was drastically decreased as the plating number was increased. The plating rate was 9 ㎛ / hr for 6 plating times. Further, nickel was precipitated in the nickel plating solution at the number of plating times of 6 times, and the nickel plating solution could not be used later.

On the other hand, in the case of the present invention, the initial plating rate was 14.2 탆 / hr, and the plating rate tended to decrease as the number of plating times increased. The plating rate was 12 ㎛ / hr for 6 plating times, and the plating rate was faster than the comparative example. In addition, the number of plating times was 6 or more. The plating rate was about 9.8 ㎛ / hr for 8 platings, and the stability of the nickel plating solution was also high.

FIG. 4 is a graph showing the amount of phosphorus deposited in the plating layer formed in the process of plating the plating object using the nickel plating solution according to the technical idea of the present invention and the nickel plating solution according to the comparative example, according to the plating number.

Referring to FIG. 4, in the case of the comparative example, the amount of vacancy of phosphorus in the plating layer in the initial plating was 8.8 wt%, but the amount of phosphorus in the phosphorus was increased as the number of plating was increased. And 10.5 wt% in 6 times of plating.

On the other hand, in the case of the present invention, the amount of vacancies in the plated layer in the initial plating was 7.5 wt%, and the amount of vacancies in the phosphorus was gradually increased as the number of plating was increased. It showed 8.4 wt% in 6 plating times and 9.0 wt% in 8 plating times. Thus, it can be seen that the nickel plating solution having an increased number of plating times can have properties similar to those of the initial nickel plating solution.

5 is a scanning electron micrograph showing the surface of the plating layer formed on the plating target object according to the number of times of plating using the nickel plating solution according to the technical idea of the present invention and the nickel plating solution according to the comparative example, respectively.

Referring to FIG. 5, in the case of the comparative example, crystal grains were hardly formed in the plating layer at the time of initial plating (one time plating), and crystal grains formed in some cases did not show definite grain boundaries. However, as the number of plating times was increased, the crystal grains formed in the plating layer became clear. When the number of times of plating is six, a plurality of pits are formed in the plating layer, which may cause corrosion at the interface of such pits and crystal grains. Therefore, in the case of the comparative example, the plating quality of the plated layer decreased sharply as the number of plating was increased.

On the other hand, in the case of the present invention, at the initial plating, crystal grains were hardly formed in the plating layer and appeared amorphous, and crystal grains were hardly formed or crystal grains were not observed even when the number of plating was increased. For example, the plating layer having the number of plating of four times is substantially similar to the plating layer of the first plating of the comparative example. It is also expected that corrosion at the interface of the crystal grain will be prevented because the crystal grains are not clear even at the number of plating times of 6 and exhibit a mixed form with the amorphous phase. Also, the pit did not appear.

6 is a scanning electron microscope (SEM) image of a plating layer formed on a copper wiring of a printed circuit board using a nickel plating solution according to the technical idea of the present invention and a nickel plating solution according to a comparative example, respectively.

Referring to FIG. 6, in the comparative example, the thickness of the plating layer on the upper portion of the copper wiring was about 11.0 μm and the lower portion was about 11.1 μm, but the corner portion was about 5.8 μm. The thickness variation was large.

On the other hand, in the case of the present invention, the thickness of the plating layer on the upper portion of the copper wiring was about 16.8 탆, the lower portion was 17.3 탆, and the corner portion was 15.8 탆. Thus, the thickness deviation was small according to the position of the plating layer, A plating layer could be realized.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the invention as defined in the appended claims. Will be apparent to those of ordinary skill in the art.

10: plating apparatus, 20: plating bath,
30: Nickel plating liquid, 40: Plated object, 50: Plated layer,

Claims (20)

A nickel metal salt providing nickel ions for plating;
A reducing agent for reducing nickel ions for plating;
A complexing agent which forms a complex with nickel ions for plating and comprises a carboxylic acid and an alpha hydroxy acid; And
A metal stabilizer which suppresses the reduction reaction of nickel ions for plating and is lead-free and cadmium-free and contains a metal element;
Lt; / RTI >
Wherein the metal stabilizer is dissolved in an alkylsulfonic acid solution in advance and added to the nickel plating solution. The lead-free and cadmium electroless nickel plating solution according to claim 1, wherein the complexing agent is contained in the range of 20 g to 40 g per 1 liter of the nickel plating solution. 2. The method of claim 1, wherein the complexing agent comprises a lead-free and cadmium-free electroless nickel plating solution containing the carboxylic acid in the range of 5g to 25g per 1 liter of the nickel plating solution and the aliphatic hydroxyl acid in the range of 5g to 20g Year nickel plating solution. The complexing agent according to claim 1, wherein the complexing agent is at least one of acetic acid, adipic acid, tartaric acid, and succinic acid derivatives of the carboxylic acid and derivatives of the aliphatic acid, citric acid, lactic acid, glycolic acid, mandelic acid, and mandelic acid. < Desc / Clms Page number 24 > The electroless nickel plating solution according to claim 1, wherein the complexing agent is a lead-free and cadmium-free electroless nickel plating solution containing 5 to 25 g of adipic acid and acetic acid per liter of the nickel plating solution and 5 to 20 g of lactic acid . The method of claim 1, wherein the complexing agent is a lead-free and cadmium-free electroless nickel plating solution containing adipic acid, acetic acid, and tartaric acid in an amount ranging from 5 g to 25 g per 1 liter of the nickel plating solution, Year nickel plating solution. The plating solution according to claim 1, wherein the complexing agent comprises adipic acid, acetic acid, and succinic acid in an amount ranging from 5 g to 25 g per 1 liter of the nickel plating solution, and further including lactic acid and glycolic acid in an amount ranging from 5 g to 20 g And Cadmium free electroless nickel plating solution. 2. The nickel plating solution according to claim 1, wherein the complexing agent comprises 5 to 25 g of adipic acid and acetic acid per 1 liter of the nickel plating solution, and 5 to 20 g of lactic acid and thiodiglycolic acid together, Cadmium free electroless nickel plating solution. The method according to claim 1, wherein the nickel metal salt comprises at least one of nickel sulfate, nickel chloride, nickel sulfamide, nickel nitrate, nickel oxide and nickel carbonate,
Wherein the nickel metal salt is contained in a range of 4 g to 7 g with respect to 1 liter of the nickel plating solution. The method of claim 1, wherein the reducing agent comprises at least one of hypophosphite, boron hydride, dimethylamine borane, and hydrazine,
Wherein the reducing agent is contained in an amount of 20 g to 35 g per 1 liter of the nickel plating solution. The method of claim 1, wherein the metal stabilizer is at least one selected from the group consisting of Tel, Te, Sb, Bi, Sn, Thl, Lead-free and Cadmium-free electroless nickel plating solution. The lead-free and cadmium electroless nickel plating solution according to claim 1, wherein the metal stabilizer comprises at least one of a metal element itself, a nickel metal salt, a metal oxide, and a metal sulfide. The lead-free and cadmium electroless nickel plating solution according to claim 1, wherein the metal stabilizer is contained in the range of 0.1 ppm to 5.0 ppm with respect to 1 liter of the nickel plating solution. delete The nickel plating solution according to claim 1, further comprising a pH adjusting agent containing at least one of sulfuric acid, hydrochloric acid, nitric acid, ammonia water, sodium hydroxide, and potassium hydroxide, and adjusting the pH of the nickel plating solution to a range of 3.5 to 5.5. Cadmium free electroless nickel plating solution. 2. The nickel plating solution according to claim 1, further comprising a sulfide-based stabilizer for inhibiting spontaneous decomposition of the nickel plating solution and preventing the precipitate formed by aging of the nickel plating solution from reacting with the reducing agent to stabilize the nickel plating solution. Lead-free and Cadmium-free electroless nickel plating solution. 17. The method of claim 16, wherein the sulfide stabilizer is selected from the group consisting of a lead free and a non-lead free, including at least one of thiourea and its derivatives, sulfite, pyrosulfite, and thiocyanate. Cadmium electroless nickel plating solution. The lead-free and cadmium electroless nickel plating solution according to claim 16, wherein the sulfide stabilizer is contained in the range of 0.1 ppm to 3.0 ppm with respect to 1 liter of the nickel plating solution. Preparing a lead-free and cadmium electroless nickel plating solution according to any one of claims 1 to 13 and 15 to 18; And
Immersing the plating target in the lead-free and non-cadmium electroless nickel plating solution to form an electroless plating layer on the plating target;
And an electroless plating method using a lead-free and cadmium-free electroless nickel plating solution. A nickel-plated layer plated on the surface of a plating target by a lead-free and cadmium-free electroless nickel plating solution according to any one of claims 1 to 13 and 15 to 18.

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